Hot gas seal

ABSTRACT

An inventive hot gas seal comprises a sealing body and means for allowing a cooling fluid, preferably cooling air, to flow through the interior of the sealing body. Such a hot gas seal can be effectively cooled by guiding a cooling fluid through the interior of the sealing body.

FIELD OF THE INVENTION

The present invention relates to a hot gas seal and a hot gas sealassembly.

BACKGROUND OF INVENTION

Walls of high temperature gas reactors, e.g. the walls of turbinecombustion chambers, need to be shielded by a suitable thermal shieldagainst attack of the hot gas. The thermal shielding can be achieved byproviding a hot gas resistant liner, which usually comprises a number ofshield elements covering the wall to be shielded. The heat shieldelements can e.g. be implemented in form of ceramic heat shield elements(CHS elements) or in form of suitable metallic heat shield elements. Toallow for thermal expansion when being exposed to the hot gas, the heatshield elements are arranged such that gaps are left between neighboringheat shield elements. In order to prevent hot gas from passing throughthese gaps from the hot gas side of a heat shield, e.g. to a carrierstructure to which the heat shield elements are fixed, gaps would needpurging with air to avoid over-heating. This air is costly leakage.

In EP 1 302 723 A1 it is proposed to seal gaps between heat shieldelements with sealing elements to prevent hot gas from passing the gaps.This sealing elements my be cooled.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a hot gas seal and ahot gas seal assembly by which the cooling of the hot gas seal can beimproved.

The first object is solved by a hot gas seal as claimed in claim 1, thesecond object is solved by a hot gas seal assembly as claimed in claim11.

An inventive hot gas seal comprises a sealing body and means forallowing a cooling fluid, preferably cooling air, to flow through theinterior of the sealing body.

Such a hot gas seal can be effectively cooled by guiding a cooling fluidthrough the interior of the sealing body.

In a first embodiment of the present invention, at least one coolingchannel is formed to extend through the interior of the sealing body assaid means for allowing a cooling fluid to flow through the interior ofthe sealing body.

In the first embodiment, the sealing body may be shaped in a tube likemanner such that it comprises a circumferential portion and an interiorspace surrounded by said circumferential portion which defines a coolingchannel for allowing a cooling fluid to flow through the interior of thetube like shaped sealing body.

In a second embodiment of the inventive hot gas seal, the sealing bodyis made from a porous material the pores of which are inter-connected sothat the pores form said means for allowing a cooling fluid to flowthrough the interior of the sealing body. Such a porous material allowsfor an effective distribution of the cooling air in the interior of thesealing body and, therefore, for evenly cooling the hot gas seal.

In an advantageous development of the second embodiment, the porousmaterial is an elastic porous material. Such a hot gas seal can be fixedbetween neighboring heat shield elements by spring forces. As theelastic porous material, a ceramic material, metal foam, or a suitablepolymer material may be used. The choice of the material to be used maydepend on the temperatures of the hot gas which is to be prevented frompassing through the gaps between two heat shield elements.

A hot gas seal assembly according to the invention comprises a hot gasseal which comprises a sealing body in which at least one coolingchannel extending through the interior of the sealing body is formed asa means for allowing a cooling fluid to flow through the interior of thesealing body. The inventive hot gas seal assembly further comprisesmeans which are arranged outside of the hot gas seal for channeling acooling fluid flow, preferably a cooling air flow, at least partlythrough the cooling channel of the hot gas seal. By providing such meansa highly efficient cooling of the hot gas seal of the assembly ispossible.

The means for channeling cooling fluid through the cooling channel maybe designed such that a high static pressure is build up in front ofthem which channels the cooling fluid at least partly through thecooling channel.

The inventive hot gas seal assembly may further comprise a meansarranged outside the hot gas seal for guiding the cooling fluid whichhas flown through the cooling channel back into the cooling fluid flow.Such a means may be designed such that a high static pressure is buildup in front of them which guides the cooling fluid back into the coolingfluid flow.

As a means for building up high static pressure, a fixing bolt forfixing a heat shield element or any other flow restriction may be used.

Further features, properties, and advantages of the present inventionare described hereinafter with reference to the accompanying drawings,by means of detailed embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of the inventive hot gas seal.

FIG. 2 shows a modification of the inventive hot gas seal of the firstembodiment.

FIG. 3 shows a further development of the inventive hot gas seal of thefirst embodiment.

FIG. 4 shows a second embodiment of the inventive hot gas seal.

FIG. 5 shows an embodiment of the inventive hot gas seal assembly.

DETAILED DESCRIPTION OF INVENTION

A first embodiment of the inventive hot gas seal is shown in FIG. 1. Thefigure shows, in a schematic fashion, a first heat shield element 10comprising a first front face 12 in which a first grove 14 is arrangedand a second heat shield element 16 having a second front face 18 inwhich a second grove 20 is arranged. The heat shield elements 10, 16 arearranged such that the first front face 12 and the second front face 18are disposed opposite to each other with the first grove 14 and thesecond grove 20 forming a space for accommodating an inventive hot gasseal 22, therein.

The hot gas seal 22 comprises a sealing body 24 which has a tube-likeshape. The interior of the sealing body 24 forms a cooling channel 26for allowing a cooling fluid, which in the present embodiment is coolingair, to flow through the hot gas seal 22. In the present embodiment, thesealing body 24 comprises a ceramic portion 28 as a highly heatresistant portion.

The hot gas seal 22 is arranged such in the space formed by the firstgrove 14 and the second grove 20 that the ceramic portion 28 showstowards the hot gas side of the liner, i.e. the sides of the heat shieldelements which are disposed to the hot gas.

Inside the cooling channel 26, an axial flow of cooling air 30 and aconvective cooling air flow which originates from the axial flow 30 andflows clockwise and counter-clockwise along the wall of cooling channeltowards the center of the ceramic portion 28 (indicated by arrows) areprovided. At the center of the ceramic portion 28, the convectivecooling air flow is directed back towards the axial cooling air flow 30.With the described hot gas seal, an effective cooling of the ceramicportion, which is disposed to the hot gas, is possible.

A modification of the first embodiment is shown in FIG. 2. Again, a hotgas seal 122 is arranged in a space formed by groves 114 and 120 whichare arranged in first and second front faces 112 and 118 of first andsecond heat shield elements 110, 116, respectively. The modificationdiffers from the first embodiment in the cross-sectional shape of thegroves 114, 120, the hot gas seal 122, and the cooling channel 126. Asshown in FIG. 2, the cross-sectional shape of the sealing body 124 andthe cooling channel 126 is chosen to be heart like with the ceramicportion 128 lying opposite to an apex like portion 123 and beingindented at its center part towards said apex like portion 123.

In the modification shown in FIG. 2, the axial cooling air flow 130takes place close to the apex like portion 123 of the cross-section ofthe cooling channel. Like in FIG. 1, a clockwise and a counter-clockwiseconvective cooling air flow (indicated by arrows) takes place along theinner walls of the sealing body 124. However, compared to thecross-sectional shape of the cooling channel in FIG. 1, the re-directionof the convective cooling air flow towards the axial cooling air flow130 is improved.

A further development of the first embodiment is shown in FIG. 3. FIG. 3shows a hot gas seal 222 comprising a sealing body 224 which forms atube with the interior of the tube forming a cooling channel 226 forallowing cooling air to flow through the hot gas seal 222. In differenceto the hot gas seals shown in FIGS. 1 and 2, the hot gas seal of FIG. 3does not comprise a ceramic portion. Instead, it comprises ceramic ormetallic balls 228 or a ceramic or metallic powder which are/is arrangedin an elastic matrix 224 which forms the sealing body. In the hot gasseal 222 shown in FIG. 3, due to the ceramic or metallic balls 228 orthe ceramic or metallic powder, the sealing body is elastic and shows agood sealing ability.

A second embodiment of the present invention is shown in FIG. 4. In FIG.4, a first heat shield element 310, a second heat shield element 312 anda hot gas seal 322 are shown in a schematic fashion. The first heatshield element 310 and the second heat shield element 318 comprise afirst front face 312 and a second front face 316, respectively. Theyfurther comprise a first hot gas side 313 and a second hot gas side 317.

In the second liner 318, a recess 320 is formed in the second front face316 at the edge to the hot gas side 317. The heat shield elements 310,318 are arranged such that the front faces 312, 316 are disposedopposite to each other and that the recess 320 forms, together with thefirst front face 312, a space for a accommodating therein the hot gasseal 322 according to the second embodiment.

Through the gap 331 between the first front face 312 and the secondfront face 316, a cooling air flow 332 outgoing from a carrier structureflows towards the hot gas side of the liner.

The sealing body 324 of the hot gas seal 322 is made from a porousmaterial the pores of which are interconnected such that they formchannels through which the cooling air of the cooling air flow 332 canpass through the hot gas seal. Thus, the cooling air can flow throughthe hot gas seal 322.

In addition, the material of the sealing body 324 is an elasticmaterial, so that the hot gas seal 322 is held in place by spring forceswhich act on the first front face 312 and the part of the recess 320which lies opposite to the first front face 312. As elastic material,all materials which are suitable for being disposed to a hot gas can beused. Examples for such materials are porous ceramics, like abradableTBC, metal foams or polymeric materials.

An embodiment for an inventive hot gas seal assembly 400 is shown inFIG. 5. The figure shows, in a schematic fashion, a heat shield element410 which is fixed by means of hooks (not shown) and fixing bolts 434,436 of a generally cylindrical cross section. The fixing bolts 434, 436are arranged in front of and behind a hot gas seal 422, e.g. a hot gasseal as described with respect to FIG. 3. Due to the high staticpressure built up in front of the fixing bolt 434, the cooling air 432is partly guided into the cooling channel of the hot gas seal 422. Afterpassing through the hot gas seal 422, the cooling air is guided backinto the cooling air flow 432 by a low static pressure built up inbehind of the fixing bolt 436.

Although in the shown embodiment for the hot gas seal assembly thefixing bolts 434, 436 are used to build up high and low static pressure,other means could be used as well as long as they allow for building upa high pressure in front of and a low pressure behind the hot gas seal422.

1. A hot gas seal comprising a sealing body and means for allowing acooling fluid to flow through the interior of the sealing body.
 2. Thehot gas seal claimed in claim 1, in which at least one cooling channelextending through the interior of the sealing body is formed as saidmeans for allowing a cooling fluid to flow through the interior of thesealing body.
 3. A hot gas seal which comprises a sealing body, thesealing body being shaped in a tube like manner such that it comprises agenerally circumferential portion and an interior space surrounded bythe circumferential portion which defines a cooling channel for allowinga cooling fluid to flow through the interior of the tube like shapedsealing body.
 4. The hot gas seal as claimed in claim 1, in which thesealing body is made from a porous material the pores of which areinterconnected so that they form said means for allowing a cooling fluidto flow through the interior of the sealing body.
 5. The hot gas seal asclaimed in claim 4, in which the porous material is an elastic material.6. The hot gas seal as claimed in claim 5, in which the elastic materialis a ceramic material.
 7. The hot gas seal as claimed in claim 5, inwhich the elastic material is a metal foam.
 8. The hot gas seal asclaimed in claim 5, in which the elastic porous material is a polymermaterial.
 9. A hot gas seal assembly comprising a hot gas seal whichcomprises a sealing body in which at least one cooling channel extendingthrough the interior of the sealing body is formed as a means forallowing a cooling fluid to flow through the interior of the sealingbody and which further comprises means arranged outside of the hot gasseal for channeling a cooling fluid flow at least partly through thecooling channel of the hot gas seal.
 10. The hot gas seal assemblyclaimed in claim 9, in which the means for channeling the cooling fluidthrough the cooling channel are designed such that a high staticpressure is built up in front of them which channels the cooling fluidat least partly through the cooling channel.
 11. The hot gas sealassembly claimed in claim 10, in which a fixing bolt for fixing a heatshield element is used for building up said high static pressure. 12.The hot gas seal assembly claimed in claim 9, comprising a meansarranged outside of the hot gas seal for guiding the cooling fluid whichhas flown through the cooling channel back into the cooling fluid flow.13. The hot gas seal assembly claimed in claim 12, in which the mans forguiding the cooling fluid back into the cooling fluid flow are designedsuch that a high static pressure is built up in front of them whichguides the cooling fluid back into the cooling fluid flow.
 14. The hotgas seal assembly claimed in claim 13, in which a fixing bolt for fixinga heat shield element is used for building up said high static pressure.